|
Pardon me for being the noob wandering into a 5 page thread, but as an owner of two turbo'd SAABs, I've had a little experience with turbos. From my experience, Johnny's right. Turbos are going to help you make more power more efficiently from a smaller motor but for day to day economical driving, you may not see a difference.
SAAB's been turbocharging production cars since 1978 and they've always played it as an economical way to make good power from a small engine. They have a rather simple boost/vacuum gauge in the instrument cluster that shows a three color coded range. The needle points to green (the economical range) when there is a vacuum. Slight boost puts the needle in the yellow range and red for higher boost. It's always been my experience that as soon as the car is taking advantage of boost pressure, economy starts dropping.
And no, turbo power isn't free. There is excess back-pressure when compared to naturally aspirated cars and that backpressure is, of course, produced from the exhaust having to be routed through the turbo vanes. That backpressure creates ridiculous heat that has to be dealt and can lead to other issues.
SAAB and VW have both dealt with sludge issues b/c of the mix of heat and extra blow-by generated by the higher compression inside the cylinders combined with low crankcase oil volume. When SAAB redesigned their bread and butter 4 cyl turbo engine in 1998 they used a simpler ring design in an attempt to provide less friction. This redesign used a PCV system completely inadequate for the job and all that turbo-induced blow-by deteriorated the oil and PCV hose rubber pretty quick, clogging oil pickup screens and leading to oil starvation. SAAB had to issue a total of 6 pcv upgrade kits before they halfway got it right for owners of 99-2003 model cars.
SAAB also tunes the ECUs to run ridiculously-rich when on-boost to avoid detonation. For certain, it's nice to have a 2.3l engine that makes 211 lb-ft of torque and 185 hp (and 260 hp in current trim on the 9-5) but when cruising my turbo is off boost and the manifold is in vacuum. And my best mpg figures are from using pretty much zero boost.
Just my personal experience. I'm no master mechanic by any means.
__________________
|